An IP Multimedia Subsystem (IMS) enables the controlled delivery of a variety of application services across a private network that supports the Internet Protocol (IP). For example, the IMS can allow a wireless service subscriber to perform voice calls on a wireless device supporting IP network connectivity, using a Voice Over IP (VOIP) protocol. This enables the wireless device to support voice calls even if the device lacks support for circuit-switching protocols traditionally required for voice calls. In the IMS paradigm, several application services (which may include VOIP, whiteboard discussions, video conferencing, push-to-talk over cellular (POC), real-time content sharing for video/audio files, instant messaging, and interactive gaming among other things) may be combined into a single SIP-based session.
Most access to online application programs from a mobile device is authenticated by some sort of login protocol. The most common login protocol requires that the user enter their user name and a password. However this technique has drawbacks. First, the user must often be required to remember a host of passwords for different application programs. In addition, user names and passwords are often hacked or stolen, thereby placing the user's data or financial security at risk. Given these problems and others, there is a need for an improved technique for providing access to online application programs from a mobile device.